Light-emitting devices are widely used for domestic, industrial, and vehicular applications. For example, a light source of a light-emitting device used in a vehicular headlamp may be a halogen (or incandescent) bulb, a high-intensity discharge (HID) lamp, a xenon lamp, a light-emitting diode (LED), or the like. In addition, there is an increasing interest in a laser diode (LD) as a next-generation light source of a light-emitting device.
Vehicular headlamps are becoming more advanced technologically, functionally, and aesthetically. Changes to light sources such that they have a reduced size while exhibiting the same energy efficiency and light output, material changes, precision injection and machining, and the like are driving this advancement. Such light sources are increased in brightness and reduced in size while evolving from a halogen bulb or an HID lamp to an LED or an LD.
The light-emitting device is not limited, in terms of the functionality thereof, merely to illuminating a dark place, but may be utilized to ensure visibility in the state in which a high beam is turned on at all times while the distribution of light thereof is controlled, or as a device for communication with pedestrians or other vehicles. In addition, in terms of the aesthetic design thereof, headlamps are becoming slimmer and are implemented not only in a linear shape but also in a curvilinear shape and the like.
In the vehicular headlamp, an additional light source module, excluding a high beam or a low beam, is connected to an element for night vision use to provide visibility at night so as to improve the safety of pedestrians or drivers. When attempting to emit light towards a subject from such an element for night vision use, it is necessary to move an entire optical system including, for example, an actuator or a motor as well as a light source. This increases power consumption and introduces limitations such as the requirement to provide a space for the movement of the optical system.